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| 型号： | MC34848EP |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 29/38页 |
| 文件大小： | 0K |
| 描述： | IC LED DVR BACKLIGHT 8CH 48QFN |
| 产品变化通告： | AMPD Product Discontinuation 12/Dec/2012 |
| 标准包装： | 260 |
| 恒定电流： | 是 |
| 恒定电压： | 是 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 8 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 频率： | 200kHz ~ 1.2MHz |
| 电源电压： | 2.6 V ~ 3.6 V |
| 输出电压： | 45V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 48-VFQFN 裸露焊盘 |
| 供应商设备封装： | 48-QFN-EP（7x7） |
| 包装： | 托盘 |
| 工作温度： | -40°C ~ 85°C |
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TYPICAL APPLICATIONS
I L =
I OUT
1 ? D
V D
Average inductor current.
Diode forward voltage drop, e.g. 0.7 V
Boost converter duty cycle,
SELECTING THE INPUT CAPACITOR FOR THE
BOOST CONVERTER
What matters most about the input capacitor selection is
its RMS current capability, ESR, and the voltage rating, more
than the value itself. As a result, when selecting the input
capacitor, the user must take into consideration:
1. The RMS current rating of the capacitor(s) should be
equal or higher than:
D
V OUT + V D ? V IN
V OUT + V D
= 0 . 46
I RMS _ IN =
I OUT
1 ? D
×
r
12
? L ? 21 μ H. An off the shelf inductor value of 22 μ H can
be used.
Note: When selecting an inductor, make sure that both the
saturation current (I SAT ) & RMS current (I RMS ) > I L + ( Δ I / 2).
The saturation current (I SAT ) is the current at which the
inductance value drops a specified amount below its
measured value with no DC current. The inductance drop is
attributed to core saturation.
The RMS current (I RMS ) is the root mean square current
that causes the temperature of the part to rise a specific
amount above 25°C ambient. The temperature rise is
attributed to I 2 R losses.
SELECTING THE OUTPUT CAPACITOR FOR THE
BOOST CONVERTER
The minimum output capacitor can be determined as
follows:
2. The lower the ESR, the lower the conduction losses
and the input ripple voltage, which implies less input
noise and EMI effects
3. The voltage rating must be at least 50% higher than
the maximum input voltage.
4. The bigger the capacitor, the smaller the input ripple
voltage. Nevertheless, the bigger the capacitor, the
higher the inrush current the input protection MOSFET
should handle, probably causing turn on failures.
SELECTING THE COMPENSATION NETWORK
COMPONENTS
As Freescale′s 34848 uses current mode control for the
boost converter output voltage regulation, the ramp to the
PWM modulator is derived from the inductor-switch current.
As a result, there is no double LC pole anymore, and a simple
Type-II network compensation is implemented by using a
Transconductance Operational Amplifier.
? V OUT
× f SW × ? ?
? ? ?
where:
C OUT =
?
? I OUT
D
? Δ V OUT
? 2 V OUT
? ?
? ?
The most common way of producing the ramp is to simply
sense the forward drop across a current sense resistor. This
small sensed voltage is then amplified by a current sense
amplifier to get the voltage ramp, which is applied to the PWM
modulator.
One of the subtleties of current mode of control is that it
needs a small ramp to the comparator ramp, which is called
Δ V OUT
Peak to peak output voltage ripple, e.g. 50 mV
slope compensation. Its purpose is to prevent an odd artifact
of current mode control called sub-harmonic instability.
? C OUT ? 23 μ F. The next bigger off the shelf capacitor
value of 33 μ F is chosen. In the case of switching power
supplies, it is a good practice to use electrolytic capacitors (to
increase the ripple current capability) and ceramic capacitors
The following design equations are presented for the
compensation network [1][2] ,
(to reduce the ESR effects) together, and consider their
capacitance value over temperature.
R COMP =
g m
A
V ref
V OUT
=
A
12 . 6528 × 10 ? 6
34848
Analog Integrated Circuit Device Data
Freescale Semiconductor
29
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MC34848EPR2 | 功能描述:LED照明驱动器 8 CHANNEL LED DRIVER RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MC34849 | 制造商:SPC Multicomp 功能描述:HEADER VERTICAL 16WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 16POS, 3MM; Series:2261(5561); Pitch Spacing:3mm; Contact Termination:Through Hole Vertical; No. of Contacts:16; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes |
| MC34851 | 制造商:SPC Multicomp 功能描述:HEADER VERTICAL 18WAY 制造商:SPC Multicomp 功能描述:HEADER, VERTICAL, 18WAY |
| MC34853 | 制造商:SPC Multicomp 功能描述:HEADER R/ANGLE 16WAY 制造商:SPC Multicomp 功能描述:HEADER, R/ANGLE, 16WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 16POS, 3MM; Series:2261(5561); Pitch Spacing:3mm; Contact Termination:Through Hole Right Angle; No. of Contacts:16; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes |
| MC34855 | 制造商:SPC Multicomp 功能描述:HEADER R/ANGLE 18WAY 制造商:SPC Multicomp 功能描述:HEADER, R/ANGLE, 18WAY |
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